1. Field of the Invention
The present invention relates to devices and methodology for detecting the presence of analytes. In particular the invention relates to such devices and methodology whereby assays may be quickly and efficiently conducted in the field using an optical reading instrument.
2. The Prior Art Scenario
There is a present and continuing need to detect a wide variety of analytes with high specificity and high sensitivity in many applications. A technique that has developed over the past 30 or more years is the use of antibody/antigen reactions to provide high specificity and sensitivity and to develop an assaying technique using the antibody/antigens to provide metering or quantitation of the concentration of the requested analyte. One common use of the antibody/antigen pair is in the construction of a reaction environment in which microscopic particles to which antibody or antigens have been chemically attached are made to agglutinate or are inhibited from agglutinating in the presence of the mating antibody/antigen and the target analyte. When an agglutination reaction occurs the microscopic particles chemically bind to each other, with the antibody/antigen molecules serving as very specific chemical binding agents, forming much larger aggregates of particles which can grow in size to become easily visible to the naked eye. The progress of the reaction may be monitored and resulting data analyzed to provide quantitative results on target analyte concentration.
One approach to monitoring the agglutination reaction is to illuminate the sample with light of some frequency band or many frequency bands and to use the interaction of the light with the reacting material to extract qualitative and/or quantitative information about the analyte(s) in question. Many such approaches have been described and they rely on a variety of properties of light interaction including light transmittance (U.S. Pat. No. 4,205,954), light scattering (Leonard T. Greenburg, Clinical Chemistry, Vol. 21, No. 9, 1975, pp. 1234-1237; U.S. Pat. No. 4,174,952 and the Periodical Molecular Immunology Vol. 17, 1980, pp. 81-92), Doppler shift spectrum broadening and light beating spectroscopy (U.S. Pat. No. 4,080,264; U.S. Pat. No. 4,446,239 and the periodical Immunochemistry, Vol. 12, 1975, pp. 349-351 and Vol. 13, 1976, pp. 955-962). Each of these approaches involves the use of complex and expensive equipment and would be very difficult to package into a portable instrument.
The method with the greatest potential for incorporation into a low cost apparatus is that described in U.S. Pat. No. 4,205,954 by Babson. However, this approach relies on a change in the transmittance of a sample during an agglutination reaction and requires that the sample be under constant agitation to achieve consistent and reliable measurements. In addition all of the approaches cited above do not describe a simple one-step user-friendly device for the collection and subsequent reaction of the unknown analyte with the requisite reagents.